SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1133 PM CST Fri Nov 06 2020 Valid 071200Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF SOUTHEAST ARIZONA... ...SUMMARY... A few strong wind gusts may accompany thunderstorms across parts of southeast Arizona later this afternoon and early evening. ...Southeast AZ/southern CA... Strong upper low is digging southeast along the central CA Coast late this evening. A significant piece of this feature is forecast to dig into the lower CO River Valley by 08/00z as 100kt+ 500mb speed max translates across the northern Baja Peninsula before ejecting into eastern AZ during the late evening. Substantial 12 hour mid-level height falls will develop ahead of this short wave, and the frontal zone that surges across the southwestern US will be sharply focused/forced in response. While boundary-layer moisture is currently limited across the southwestern deserts, surface dew points are notably higher south of the international border. Low-level trajectories will become more favorable for some of this moisture to advance north ahead of the front. If adequate moisture can return to southeast AZ ahead of the wind shift, scattered robust convection could develop. Latest CAMs support at least isolated thunderstorm activity and forecast soundings favor gusty winds given the steep lapse rates and strong flow that will spread across this region. Although SBCAPE will not be that significant, vertical mixing and fast storm motions will favor gusty winds. For these reasons have introduced 5 percent wind probabilities with thunderstorms that develop ahead of the cold front. This activity will spread rapidly northeast into northwest NM/south-central CO, possibly in the form of a weak squall line. Given the limited buoyancy it's not clear the threat of damaging winds will extend into this region. Upstream across southern CA, very cold mid-level temperatures will overspread this region by 18z. Forecast soundings near the southern CA Coast exhibit SBCAPE near 450 J/kg within this post-frontal regime. While severe hail is unlikely, profiles appear favorable for at least small hail within the strongest updrafts. ..Darrow.. 11/07/2020
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